The primary goal of this work is to understand the molecular mechanism by which the Transcription Factor IIIA (TFIIIA) gene is developmentally regulated. The studies to date have concentrated on the identification of cis-elements required for the expression of the TFIIIA gene in immature oocytes, mature oocytes and somatic cells. Eight or more of these cis-elements have been identified, several of which appear to be developmentally regulated. The developmentally regulated elements are functionally expressed at different times, one is specific for immature oocytes and the others (several negative and one positive) are "embryo-specific" (not functional in oocytes). The times at which these factors are regulated correspond to times in development when TFIIIA mRNA levels change (10-fold more TFIIIA mRNA in immature oocytes than in mature oocytes and approximately 10-5 more TFIIIA mRNA in mature oocytes than in post-gastrula embryos). The investigator has identified trans-acting factors which bind to most of these elements and have obtained putative cDNA clones for one of the developmentally regulated factors (the one which binds to the immature oocyte-specific element). This proposal concentrates on expanding the results on the interactions between these elements and the further characterization of factors which bind to these elements. The investigator proposes to isolate the various trans-acting factors and/or isolate cDNA clones encoding these factors. These cDNA clones will then provide one with molecular probes for these factors. The functions of these factors and interactions between them and other transcription factors will then be examined using in vivo and in vitro approaches. Qualitative and quantitative differences in the structure, activity, and interactions of these factors will be determined at various times during development.